Protective effects of silymarin on renal ischemia-reperfusion injury

Abstract

Objective To explore the protective effect of silymarin on renal ischemia- reperfusion(I/ R)injury. Methods Twenty- four male C57BL/6 mice were randomly divided into three groups(n= 8): Sham,I/R,silymarin+ I/R.In Sham group, the animals were subjected to only incision of abdominal cavity and separation of bilateral renal pedicle.In silymarin+ I/R group, the animals were administered with 100 mg/kg dose of silymarin daily intragastrically.In I/R group, the animals were administered with normal saline + 0. 1% ethanol daily intragastrically.Seven consecutive days before surgery, the animals in silymarin+ I/R group and I/R group were subjected to a standard renal ischemia to induce acute kidney injury(AKI)after 45 min of bilateral renal artery clamping.Serum creatinine(SCr)and blood urea nitrogen(BUN) were determined.The renal injury was observed by distribution of periodate schiff(PAS) staining. Myeloperoxidase (MPO)activity in renal tissues was measured.The expression of CD68 was detected by immunofluorescence. The secretion of inflammatory factors in renal tissues was measured by enzyme- linked immunosorbent assay (ELISA).The apoptosis was tested by Td T- mediated d UTP nick end labeling(TUNEL).The expression of Cleaved- Caspase- 3, B- cell lymphoma/Leukemia- 2(bcl- 2)and bax proteins was detected by Western blotting. Results SCr and BUN levels in I/R group[(22. 7±1. 2),and(1 295. 7±64. 2)mg/L]were significantly higher than in silymarin+ I/R group[(14. 0±3. 9), and(571. 7±17. 0) mg/L, P<0. 05]and Sham group[(4. 4±0. 2),and(291. 7±17. 7)mg/L](P<0. 05).Renal tubular injury scores in Sham, and silymarin+ I/R groups(1. 75±0. 16)were significantly lower than in I/R group(4. 17±0. 29).The MPOactivity in I/R group[(52. 0±6. 3) U/g] was higher than in silymarin+ I/R group[(31. 8±5. 4) U/g](P< 0. 05).The expression of CD68 and secretion of inflammatory factors in I/R group were significantly increased as compared with sham group and silymarin+ I/R group(P<0. 05).The number of apoptotic cells in silymarin+ I/R group was less than in I/R group(P<0. 05).The Cleaced- Caspase- 3 and bax expression in I/R group was higher than in sham group and silymarin+ I/R group, but bcl- 2 expression in I/R group was lower than in silymarin+ I/R group(P< 0. 05). Conclusion Silymarin reduced expression of inflammatory factors and neutrophil and macrophage infiltration in the process of renal I/R,alleviated renal tubular injury, and inhibited apoptosis so as to achieve protective effects on renal I/R injury. Key words: Silymarin; Renal ischemic; Reperfusion injury; Renal function